1. Field of the Invention
The present invention relates to an ink jet recording head for recording data by discharging ink and a manufacture method for the ink jet recording head.
2. Related Background Art
As an ink jet recording head to be used for an ink jet recording system for recording data by discharging ink, a so-called “side shooter type recording head” is known which discharges an ink droplet along a direction perpendicular to a substrate formed with ink discharge energy generating elements.
As a liquid discharge method for this recording head, the specification of U.S. Pat. No. 6,155,673 discloses the structure that an ink droplet is discharged when a bubble formed by heating a heat generating resistor member communicates with external air. According to this discharge method, small droplet recording can be realized easily and recent high precision recording requirements are satisfied.
The structure of a “side shooter type recording head” is known by which ink is supplied from the bottom of a substrate to discharge pressure generating elements via a supply port and a common flow path and separate flow paths. As a manufacture method for an ink jet recording head having this structure, for example, the specification of U.S. Pat. No. 6,139,761 discloses a method of forming an ink supply port in a device substrate by anisotropical etching.
Recent needs are to develop a head which has a long train of orifices and can draw a large area at one scan. As the orifice train is elongated, the ink supply port becomes long correspondingly. As the ink supply port is simply elongated as a through hole formed through a device substrate, rigidity of the device substrate is lowered considerably. As the rigidity of the device substrate lowers, there is a risk of breaking the substrate during manufacture of an ink jet recording head and influencing a manufacture yield. In order to raise the rigidity of a device substrate, the size of the device substrate may be increased. However, a large substrate size reduces the number of heads to be manufactured from one wafer, resulting in a cost increase.
Japanese Patent Application Laid-open No. 2003-039692 discloses the structure that an ink supply port is divided into a plurality of ports by using beams. FIG. 8A is a partially transmissive plan view showing an example of an ink jet recording head with a plurality of divided ink supply ports, FIG. 8B is a cross sectional view taken along line 8B-8B of FIG. 8A, FIG. 8C is a cross sectional view taken along line 8C-8C of FIG. 8A, and FIG. 8D is a cross sectional view taken along line 8D-8D of FIG. 8A. An ink jet recording head 300 shown in FIGS. 8A, 8B, 8C and 8D has the structure that a plurality of beam portions 311a are formed in a single, long ink supply port 311 formed in a substrate 301, and this structure is very effective for retaining the rigidity of the substrate 301. However, as the ink supply port 311 is divided by the beam portions 311a, a separate flow path 306 (communicating with a common flow path 308 and corresponding to each discharge pressure generating element 305) positioned between ink supply ports 311, i.e., near at the beam portion 311a has an insufficient ink supply, so that ink refill is delayed more than other separate flow paths 306 formed at positions remote from the beam portion 311a. 
Japanese Patent Application Laid-open No. H06-115075 proposes that a bottom region of a common flow path on the surface of a substrate is etched widely to form a groove and a supply port communicating with the groove is formed. With this groove, it is expected that the supply port can be shortened and the supply port can be broadened correspondingly to improve ink refill for all separate flow paths and that a difference between ink refill due to a different relative position to the supply port can be relaxed. With this method, it is necessary to form a deeper groove in order to sufficiently relax the ink refill difference. However, as the groove is formed deeper in a wide region, the strength and rigidity of the substrate are lowered. The lowered strength of the substrate may cause breakage of the head during manufacture processes, resulting in a degraded yield. As the substrate rigidity is lowered, deformation of the substrate becomes large during manufacture processes or in use, so that ink discharge directions vary among orifices and the image quality is degraded.
In order to form a supply port at a good precision, the supply port is formed in some cases by dry etching such as reactive ion etching (RIE). Generally, although dry etching provides a high precision, it has disadvantage in terms of tact as compared to other etching processes because of single wafer processing and a low etching rate. In order to overcome the disadvantages, a substrate as thin as possible, to the extent that the strength and rigidity of the substrate are ensured, is prepared, or a substrate is thinned by grinding, wet etching or the like having a high processing performance. Thereafter, the supply port is formed by dry etching. In this case, if a groove is formed in a wide range on the bottom of the common flow path, the groove cannot be sufficiently deep in order to maintain the strength and rigidity of the substrate, so that the advantages of the groove cannot be obtained.
This method is associated with some issue of manufacture processes. For example, a method has been proposed to set a distance between the discharge pressure generating element and an orifice at a high precision and with good reproductivity by forming a flow path mold, a flow path wall and an orifice plate by solvent coating. However, if solvent coating is performed after the groove is formed deeply in a wide range of the substrate, the flow path mold and orifice plate have a saucer shape tracing the groove shape. Even if the groove is formed on the substrate, the orifice plate as the ceiling of the flow path has the saucer shape in conformity with the groove, so that the expected advantages cannot be obtained.